The present invention concerns a press which is particularly suitable for the production of precision moldings from pulverized materials, but which lends itself to use in other applications, such as the molding of plastics and the deep-drawing, swaging and stamping of metals.
The basis on which the present invention proceeds is a mechanical press having a base frame supporting a movable draft frame and a fixed platen, coupled to one another by a drive toggle for relative movement to constitute the main press ram acting on the so-called principal guide axis. Associated therewith, in accordance with the invention, are one or more hydraulically-operated auxiliary axes whose operation is adjustably timed and regulated in response to movement of the ram on the principal axis.
Automatic hydraulic presses for the production of precision moldings from pulverized materials are already known, which can also be employed for the production of complex moldings, especially moldings of single or multiple stepped configuration (see document DE-OS 31 42 126, for example). For each molding step, the actual pressing tool operates on its own molding axis which is assigned to a special hydraulic drive unit inside the press, so that a different working path relative to the pressing tool is followed and/or must be controlled by each hydraulic drive unit as it moves between its charging and operating positions.
In such types of automatic presses, mainly on account of the shape of the molding to be produced, the movement pattern between the individual hydraulic drives will necessarily be somewhat complex, and such a movement pattern can only be actuated and monitored with the help of complicated electronic control systems.
However, the systems provided in any of the known types of automatic hydraulic presses are not capable of ensuring that the movements of the various hydraulic drives are actually carried out in each molding operation in a precisely coordinated way. In particular, there is no means of ensuring consistent maintenance of the hydraulic fluid supply to the various hydraulic units at continuous, precise quantities and rates because pressure compounding is a frequent occurrence. As a result, undefined compound movements of the hydraulic drives will occur and these cannot be compensated by the electronic control system, and can have an adverse effect upon molding quality.
A further disadvantage of known types of automatic hydraulic presses is the relatively long stroke of all of the hydraulic drives, which allows only relatively limited stroke rates, constituting a further constraint on productivity.